php - check the existing of a inserted data in 1st table, if inserted data exist in the 1st table then add data into second table otherwise not inserted -

in php using mysqli first want check existing of inserted data in first table , if inserted data exist in first table add inserted data second table otherwise not inserted?

how can this?

for simplifying:

you can consist unique key each value , test key in table1 if exists insert data table 2.